Project Summary/Abstract Adult health in mid to later life in the US has been declining. Marital functioning is an important determinant of adult health and wellbeing in different-gender couples, and changes to marital functioning over the past 40 years may be a critical mechanism underlying the US adult health decline. Scholars have argued that marital functioning has declined over the past forty years, yet there is no research to support this claim. The recent legalization of same-gender marriage for all means that the marital population has expanded and diversified in ways scholars have yet to understand, and it is likely this population will grow as more same-gender partnerships transition to marriage. Due to a lack of data and power, the associations between marital functioning and health outcomes for individuals in same-gender marriages has received little attention. This project will identify key changes in marital functioning and individual health and wellbeing in the U.S. over the past four decades in different gender spouses, and benchmark these for same-gender spouses. Our approach will be to generate a third repeated cross-section (i.e. a third wave) of the Work and Family Life Study data, complementing and extending cross-sectional data collected in 1980 and 2000. We propose: Aim 1. Identify age, period, and cohort trends in marital functioning (e.g. marital happiness and conflict, divorce proneness) over the past 40 years among different gender spouses, and test for race and social class differences. Aim 2. Examine age, period, and cohort trends in the association between marital functioning and adult physical and mental health over the past 40 years among different gender couples, by race and social class. Aim 3. Examine the association between marital functioning and adult physical and mental health in individuals in same-gender marriages by race and social class, and compare the magnitude of these associations with individuals in different-gender marriages. To examine Aims 1 and 2, we will collect a third cross-section of data of the Work and Family Life Study, approximately 40 and 20 years after the first and second cross-sections. Population-representative data will be collected from 2000 individuals, ages 18 to 55, in different-gender marriages. To examine Aim 3, we will collect data from 300 women and 300 men in same-gender marriages. Data will be collected via phone and online. The primary significance of this project is 1) evidence that marital functioning has declined over the past 40 years, and the identification of declining marital functioning as a mechanism underlying declines in adult physical and mental health, and 2) the establishment of an association between poor marital functioning and poor physical and psychological health and health behaviors in same-gender marriages across race and social class. The proposed research is innovative because 1) it is a substantial departure from available U.S. data on marital functioning and health across cohorts and periods for different-gender spouses, and 2) it will benchmark marital functioning and health for married sexual minorities in the US. These data, the largest population- based sample of individuals in same and different-gender marriages to date, will be available through ICPSR.